Biomedical subjects

Alexander Y Rudensky

Publications and source records attributed to Alexander Y Rudensky.

At least 19 recordsLinked to original sources

PubMed2026

Metadomain and metaloop genome interactions in mammalian T cells.

Recent studies have advanced understanding of chromosomal organization and its role in gene regulation, yet most analyses focus on short-range interactions (<2 Mb), limiting insight into broader architecture. The relationships between topologically associating domains (TADs), sub-TAD loops, cross-TAD interactions, and chromosomal compartmentalization remain poorly understood. Here, using high-resolution Hi-C analysis, we identify extensive multi-megabase and interchromosomal interactions (metaloops) in T lymphocytes that organize into meta-TAD associations (metadomains). These metaloops connect distal promoters and regulatory elements of genes functionally important in T cells, including Ctla4, Ikzf2, Il2ra, Ets1, and Foxo1. Reanalysis of mouse and human datasets confirms their reproducibility and dependence on superenhancers. Genome-wide clustering reveals three distinct interchromosomal hubs, including a superenhancer-enriched hub linked to T cell-specific gene activation. Integrative analysis of regulatory genomics data identifies factors associated with short- versus long-range interactions. This study introduces a broadly applicable computational framework and reveals features of T cell genome organization.

Animals↗

PubMed2007

Foxp3-dependent programme of regulatory T-cell differentiation.

Regulatory CD4+ T cells (Tr cells), the development of which is critically dependent on X-linked transcription factor Foxp3 (forkhead box P3), prevent self-destructive immune responses. Despite its important role, molecular and functional features conferred by Foxp3 to Tr precursor cells remain unknown. It has been suggested that Foxp3 expression is required for both survival of Tr precursors as well as their inability to produce interleukin (IL)-2 and independently proliferate after T-cell-receptor engagement, raising the possibility that such 'anergy' and Tr suppressive capacity are intimately linked. Here we show, by dissociating Foxp3-dependent features from those induced by the signals preceding and promoting its expression in mice, that the latter signals include several functional and transcriptional hallmarks of Tr cells. Although its function is required for Tr cell suppressor activity, Foxp3 to a large extent amplifies and fixes pre-established molecular features of Tr cells, including anergy and dependence on paracrine IL-2. Furthermore, Foxp3 solidifies Tr cell lineage stability through modification of cell surface and signalling molecules, resulting in adaptation to the signals required to induce and maintain Tr cells. This adaptation includes Foxp3-dependent repression of cyclic nucleotide phosphodiesterase 3B, affecting genes responsible for Tr cell homeostasis.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2007

Maintenance of the Foxp3-dependent developmental program in mature regulatory T cells requires continued expression of Foxp3.

The transcription factor Foxp3 is required for the development of regulatory T cells (T(reg) cell). Here we report that induced ablation of a loxP-flanked Foxp3 allele in mature T(reg) cells resulted in the loss of their suppressive function in vivo and acquisition of the ability to produce interleukin 2 and T helper type 1 cytokines. Furthermore, after adoptive transfer in the absence of functional T(reg) cells into lymphopenic hosts, T(reg) cells with deletion of Foxp3 proliferated and were predominant among tissue-infiltrating T cells. In agreement with those results, we found deregulation of Foxp3 target gene expression after Foxp3 deletion. Thus, continued Foxp3 expression in mature T(reg) cells is needed to maintain the transcriptional and functional program established during T(reg) cell development.

Adoptive Transfer↗

PubMed2006

Regulatory T cells prevent catastrophic autoimmunity throughout the lifespan of mice.

Mice lacking the transcription factor Foxp3 (Foxp3(-)) lack regulatory T (T(reg)) cells and develop fatal autoimmune pathology. In Foxp3(-) mice, many activated effector T cells express self-reactive T cell receptors that are expressed in T(reg) cells in wild-type mice. Thus, in wild-type mice, most self-reactive thymocytes escaping negative selection are diverted into the T(reg) lineage, and whether T(reg) cells are critical in self-tolerance in wild-type mice remains unknown. Here, acute in vivo ablation of T(reg) cells demonstrated a vital function for T(reg) cells in neonatal and adult mice. We suggest that self-reactive T cells are continuously suppressed by T(reg) cells and that when suppression is relieved, self-reactive T cells become activated and facilitate accelerated maturation of dendritic cells.

Aging↗

PubMed2006

FOXP3 and NFAT: partners in tolerance.

Regulatory T cells suppress autoimmune responses to self-antigens. Recent studies, including one in this issue of Cell (Wu et al., 2006), suggest that the ability of T cells to choose between launching a productive immune response, functional inactivation, or developing into regulatory T cells depends upon the interplay of the key transcriptional regulators FOXP3 and NFAT.

Amino Acid Sequence↗

PubMed2006

Single-cell analysis of normal and FOXP3-mutant human T cells: FOXP3 expression without regulatory T cell development.

Forkhead winged-helix transcription factor Foxp3 serves as the dedicated mediator of the genetic program governing CD25+CD4+ regulatory T cell (T(R)) development and function in mice. In humans, its role in mediating T(R) development has been controversial. Furthermore, the fate of T(R) precursors in FOXP3 deficiency has yet to be described. Making use of flow cytometric detection of human FOXP3, we have addressed the relationship between FOXP3 expression and human T(R) development. Unlike murine Foxp3- T cells, a small subset of human CD4+ and CD8+ T cells transiently up-regulated FOXP3 upon in vitro stimulation. Induced FOXP3, however, did not alter cell-surface phenotype or suppress T helper 1 cytokine expression. Furthermore, only ex vivo FOXP3+ T(R) cells persisted after prolonged culture, suggesting that induced FOXP3 did not activate a T(r) developmental program in a significant number of cells. FOXP3 flow cytometry was also used to further characterize several patients exhibiting symptoms of immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) with or without FOXP3 mutations. Most patients lacked FOXP3-expressing cells, further solidifying the association between FOXP3 deficiency and immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome. Interestingly, one patient bearing a FOXP3 mutation enabling expression of stable FOXP3(mut) protein exhibited FOXP3(mut)-expressing cells among a subset of highly activated CD4+ T cells. This observation raises the possibility that the severe autoimmunity in FOXP3 deficiency can be attributed, in part, to aggressive T helper cells that have developed from T(R) precursors.

Animals↗

PubMed2006

In vivo sites and cellular mechanisms of T reg cell-mediated suppression.

Regulatory CD4 T (T reg) cells control immune responses to self-antigens and pathogens. However, where T reg cells act to curtail effector T cells in vivo and what stage of effector T cell activation or differentiation is targeted by T reg cells remain unknown. Furthermore, a requirement for direct effector T cell-T reg cell contact in vivo has not been ascertained. Varying answers to these important questions have been provided by several new studies.

Animals↗

PubMed2006

An intersection between the self-reactive regulatory and nonregulatory T cell receptor repertoires.

The relationship between the T cell receptor (TCR) repertoires used by self-reactive transcription factor Foxp3-positive (Foxp3(+)) CD4(+) regulatory T cells (T(reg) cells) and nonregulatory T cells with autoimmune potential is unclear. Here we found that the TCR repertoire of thymic T(reg) cells in TCRbeta-transgenic mice was diverse and was more similar to that of peripheral T(reg) cells than that of nonregulatory T cells, suggesting that thymic T(reg) cells make a substantial contribution to the peripheral T(reg) cell population. Activated T cells in Foxp3-deficient mice, which lack T(reg) cells, 'preferentially' used TCRs found in the TCR repertoire of T(reg) cells in Foxp3-sufficient TCRbeta-transgenic mice, suggesting that these self-reactive TCRs contribute to the pathology of Foxp3-deficient mice. Our analyses suggest that T(reg) cells and potentially pathogenic autoimmune T cells use overlapping pools of self-reactive TCRs.

Amino Acid Sequence↗

PubMed2006

Cellular mechanisms of fatal early-onset autoimmunity in mice with the T cell-specific targeting of transforming growth factor-beta receptor.

Transforming growth factor-beta (TGF-beta) has been implicated in the control of differentiation and proliferation of multiple cell types. However, a role for TGF-beta in the control of immune homeostasis is not fully understood because of its pleiotropic action. Here we report that complete ablation of the TGF-beta signaling in T cells engendered aggressive early-onset, multiorgan, autoimmune-associated lesions with 100% mortality. Peripheral CD4+ and CD8+ T cells with TGF-beta-receptor II (TGF-betaRII) deficiency activated cytolytic and T helper 1 (Th1) differentiation program in a cell-intrinsic T cell receptor (TCR)-specific fashion. Furthermore, TGF-betaRII deficiency blocked the development of canonical CD1d-restricted NKT cells. Instead, it facilitated generation of a highly pathogenic T cell subset exhibiting multiple hallmarks of NK cells and sharply elevated amounts of FasL, perforin, granzymes, and interferon-gamma. Thus, TGF-beta signaling in peripheral T cells is crucial in restraining TCR activation-dependent Th1, cytotoxic, and NK cell-like differentiation program which, when left unchecked, leads to rapidly progressing fatal autoimmunity.

Animals↗

PubMed2005

A function for interleukin 2 in Foxp3-expressing regulatory T cells.

Regulatory T cells (T(reg) cells) expressing the forkhead family transcription factor Foxp3 are critical mediators of dominant immune tolerance to self. Most T(reg) cells constitutively express the high-affinity interleukin 2 (IL-2) receptor alpha-chain (CD25); however, the precise function of IL-2 in T(reg) cell biology has remained controversial. To directly assess the effect of IL-2 signaling on T(reg) cell development and function, we analyzed mice containing the Foxp3(gfp) knock-in allele that were genetically deficient in either IL-2 (Il2(-/-)) or CD25 (Il2ra(-/-)). We found that IL-2 signaling was dispensable for the induction of Foxp3 expression in thymocytes from these mice, which indicated that IL-2 signaling does not have a nonredundant function in the development of T(reg) cells. Unexpectedly, Il2(-/-) and Il2ra(-/-) T(reg) cells were fully able to suppress T cell proliferation in vitro. In contrast, Foxp3 was not expressed in thymocytes or peripheral T cells from Il2rg(-/-) mice. Gene expression analysis showed that IL-2 signaling was required for maintenance of the expression of genes involved in the regulation of cell growth and metabolism. Thus, IL-2 signaling seems to be critically required for maintaining the homeostasis and competitive fitness of T(reg) cells in vivo.

Animals↗

PubMed2005

Developmental regulation of Foxp3 expression during ontogeny.

Thymectomy of neonatal mice can result in the development of autoimmune pathology. It has been proposed that thymic output of regulatory T (T reg) cells is delayed during ontogeny and that the development of autoimmune disease in neonatally thymectomized mice is caused by the escape of self-reactive T cells before thymectomy without accompanying T reg cells. However, the kinetics of T reg cell production within the thymus during ontogeny has not been assessed. We demonstrate that the development of Foxp3-expressing T reg cells is substantially delayed relative to nonregulatory thymocytes during ontogeny. Based on our data, we speculate that induction of Foxp3 in developing thymocytes and, thus, commitment to the T reg cell lineage is facilitated by a signal largely associated with the thymic medulla.

Age Factors↗

PubMed2005

Analysis of the underlying cellular mechanisms of anti-CD154-induced graft tolerance: the interplay of clonal anergy and immune regulation.

Although it has been shown that CD4(+)CD25(+) regulatory T cells (T(reg)) contribute to long-term graft acceptance, their impact on the effector compartment and the mechanism by which they exert suppression in vivo remain unresolved. Using a CD4(+) TCR transgenic model for graft tolerance, we have unveiled the independent contributions of anergy and active suppression to the fate of immune and tolerant alloreactive T cells in vivo. First, it is shown that anti-CD154-induced tolerance resulted in the abortive expansion of the alloreactive, effector T cell pool. Second, commensurate with reduced expansion, there was a loss of cytokine production, activation marker expression, and absence of memory T cell markers. All these parameters defined the tolerant alloreactive T cells and correlated with the inability to mediate graft rejection. Third, the tolerant alloreactive T cell phenotype that is induced by CD154 was reversed by the in vivo depletion of T(reg). Reversal of the tolerant phenotype was followed by rapid rejection of the allograft. Fourth, in addition to T(reg) depletion, costimulation of the tolerant alloreactive T cells or activation of the APC compartment also reverted alloreactive T cell tolerance and restored an activated phenotype. Finally, it is shown that the suppression is long-lived, and in the absence of anti-CD154 and donor-specific transfusion, these T(reg) can chronically suppress effector cell responses, allowing long-lived graft acceptance.

Amino Acid Sequence↗

PubMed2005

TGF-beta1 maintains suppressor function and Foxp3 expression in CD4+CD25+ regulatory T cells.

Transforming growth factor (TGF)-beta1 is a major pluripotential cytokine with a pronounced immunosuppressive effect and its deficiency results in lethal autoimmunity in mice. However, mechanisms of its immunosuppressive action are not completely understood. Here, we report that TGF-beta1 supports the maintenance of Foxp3 expression, regulatory function, and homeostasis in peripheral CD4(+)CD25(+) regulatory T (T reg) cells, but is not required for their thymic development. We found that in 8-10-d-old TGF-beta1-deficient mice, peripheral, but not thymic, T reg cells are significantly reduced in numbers. Moreover, our experiments suggest that a defect in TGF-beta-mediated signaling in T reg cells is associated with a decrease in Foxp3 expression and suppressor activity. Thus, our results establish an essential link between TGF-beta1 signaling in peripheral T reg cells and T reg cell maintenance in vivo.

Animals↗

PubMed2005

Cathepsin S controls MHC class II-mediated antigen presentation by epithelial cells in vivo.

Epithelial cells at environmental interfaces provide protection from potentially harmful agents, including pathogens. In addition to serving as a physical barrier and producing soluble mediators of immunity, such as cytokines or antimicrobial peptides, these cells are thought to function as nonprofessional APCs. In this regard, intestinal epithelial cells are particularly prominent because they express MHC class II molecules at the site of massive antigenic exposure. However, unlike bone marrow-derived professional APC, such as dendritic cells or B cells, little is known about the mechanisms of MHC class II presentation by the nonprofessional APC in vivo. The former use the lysosomal cysteine protease cathepsin S (Cat S), whereas thymic cortical epithelial cells use cathepsin L (Cat L) for invariant chain degradation and MHC class II maturation. Unexpectedly, we found that murine Cat S plays a critical role in invariant chain degradation in intestinal epithelial cells. Furthermore, we report that nonprofessional APC present a class II-bound endogenous peptide to naive CD4 T cells in vivo in a Cat S-dependent fashion. These results suggest that in vivo, both professional and nonprofessional MHC class II-expressing APC use Cat S, but not Cat L, for MHC class II-mediated Ag presentation.

Animals↗

PubMed2005

Regulatory T cell lineage specification by the forkhead transcription factor foxp3.

Regulatory T cell-mediated dominant tolerance has been demonstrated to play an important role in the prevention of autoimmunity. Here, we present data arguing that the forkhead transcription factor Foxp3 acts as the regulatory T cell lineage specification factor and mediator of the genetic mechanism of dominant tolerance. We show that expression of Foxp3 is highly restricted to the subset alphabeta of T cells and, irrespective of CD25 expression, correlates with suppressor activity. Induction of Foxp3 expression in nonregulatory T cells does not occur during pathogen-driven immune responses, and Foxp3 deficiency does not impact the functional responses of nonregulatory T cells. Furthermore, T cell-specific ablation of Foxp3 is sufficient to induce the identical early onset lymphoproliferative syndrome observed in Foxp3-deficient mice. Analysis of Foxp3 expression during thymic development suggests that this mechanism is not hard-wired but is dependent on TCR/MHC ligand interactions.

Animals↗

PubMed2005

A well adapted regulatory contrivance: regulatory T cell development and the forkhead family transcription factor Foxp3.

The random generation of antigen receptors in developing lymphocytes results in a considerable risk of autoimmunity. Regulatory T cells (T(reg) cells) act in a dominant, trans-acting way to actively suppress immune activation and maintain immune tolerance. Here, we discuss the principal advances in our understanding of the molecular mechanisms of T(reg) cell development and function with particular emphasis on the forkhead transcription factor Foxp3. Accumulating evidence suggests that T(reg) cells represent a dedicated T cell lineage and that Foxp3 functions as the T(reg) cell lineage specification factor. The aggressive early-onset lymphoproliferative syndrome resulting from Foxp3 deficiency identifies T(reg) cells as vital mediators of immunological tolerance to self and Foxp3 as the mediator of the genetic mechanism of dominant tolerance.

Animals↗

PubMed2005

The lysosomal cysteine proteases in MHC class II antigen presentation.

The endosomal pathway of antigen presentation leads to the display of peptides on major histocompatibility complex (MHC) class II molecules at the cell surface of antigen-presenting cells (APCs). The pathway involves two major steps, invariant chain degradation and antigen processing, which take place in the late endosomes/lysosomes. So far, of the known lysosomal proteases, only cathepsin L and cathepsin S have been shown to have a non-redundant role in endosomal presentation in vivo. Besides being engaged in the degradation of invariant chain, these enzymes also mediate the processing of antigens in distinct cell types. Surprisingly, these enzymes are active in different types of APCs, and this defined expression pattern seems to be enforced by regulatory mechanisms acting on multiple levels.

Animals↗

PubMed2004

Targeting of inducible costimulator (ICOS) expressed on alloreactive T cells down-regulates graft-versus-host disease (GVHD) and facilitates engraftment of allogeneic bone marrow (BM).

Inducible costimulator (ICOS), a CD28/cytotoxic T lymphocyte antigen 4 (CTLA-4) family member, is expressed on activated T cells. ICOS ligand, a B7 family member, is constitutively expressed on B cells, macrophages, and dendritic cells and is up-regulated on antigen-presenting cells (APCs) and some nonlymphoid tissues by tumor necrosis factor alpha (TNFalpha) or lipopolysaccharide (LPS). Thus, ICOS: ICOS ligand (ICOSL) blockade could reduce alloreactive T cell-APC interactions responsible for graft-versus-host disease (GVHD) and bone marrow (BM) graft rejection. ICOS blockade, achieved with ICOS-/- mice or anti-ICOS monoclonal antibody (mAb) administration, resulted in significant inhibition of GVHD in multiple strain combinations whether mediated by CD4+ and/or CD8+ T cells, alloantigen-specific T-cell receptor (TCR) transgenic (Tg) T cells, or CD28-, T helper 1 (Th1)-, or Th2-deficient T cells. Anti-ICOS significantly delayed GVHD mortality even when mAb infusions were delayed until day 5 after transplantation. ICOS blockade reduced the number of alloantigen-specific effector cells but did not prevent their activation. Imaging of green fluorescent protein-positive (GFP+) effectors indicated that ICOS blockade inhibited expansion of GVHD-causing effector T cells in secondary lymphoid and GVHD target organs. Engraftment rates were significantly higher in ICOS-/- versus wild-type (WT) mice receiving allogeneic BM, and ICOS blockade significantly inhibited expansion of host antidonor alloantigen-specific BM graft-rejecting T cells. These data suggest that the ICOS pathway may be a beneficial therapeutic target for GVHD inhibition, GVHD therapy, and BM graft promotion.

Animals↗